Hydraulic fracturing, also commonly referred to as “hydrofracking,” is a technique used in the removal of oil and natural gas from reservoirs contained in subsurface rock formations. Hydraulic fracturing works by increasing the pressure in the formation rock so that fractures form, creating a pathway through which oil and gas can travel to the well bore. Hydraulic fractures are typically created by pumping a fracturing fluid into a wellbore at a rate sufficient to increase the pressure downhole to an amount that exceeds the fracture strength of the formation rock. The increased pressure due to the high-pressure pumping of the fracturing fluid causes cracks to form in the formation rock. The fracturing fluid can then enter the cracks and extend the cracks further into the formation. Solid proppant is typically added to the fracture fluid to keep the cracks open.
The solid proppant is often a silica-containing material, such as silica sand or resin coated silica sand. Large amounts of dust are created and released into the atmosphere when proppant is prepared for use in the hydrofracking process. During preparation, large amounts of proppant are trucked into the drill site by pneumatic tankers. The proppant is then blown from the pneumatic tanker into proppant storage trailers known as “sand chiefs,” “sand hogs,” “sand kings,” “mountain movers,” or “frac sanders.” The top of the proppant storage trailers incorporate a series of vent hatches which vent pressurized air as the proppant is pumped into the storage trailer. As the air is vented through the top of the storage trailer, large amounts of silica-containing dust blow out the vent hatches. The flow of dust through the vent hatches creates large dust clouds when storage trailers are filled with proppant. The dust clouds obscure vision and may create an inhalation hazard for workers at the well site.
Presently, the only method for reducing the flow of dust through the storage trailer vent hatches is use of a loose-fitting fabric filter bag that is attached to the access door. The fabric filter bag is shaped like a garbage bag that inflates with air and stands upright when proppant is loaded onto the storage trailer. The fabric filter bags are undesirable because the loose fit often causes the filter bag to be completely or partially blown off the vent hatch, allowing large amounts of dust to escape. The bags are also easily blown off the vent hatch because the bag stands upright when inflated. Additionally, use of the loose-fitting fabric filter bags is disfavored because the bags make it impossible for workers to look down into the vent hatch to monitor the amount of proppant being pumped into the storage trailer. Because of the drawbacks of the loose-fitting fabric filter bags, employees of many hydrofracking operations choose to use no filter device on proppant storage trailer vent hatches, allowing large amounts of dust to be emitted.
Accordingly, there remains a need for a filter device that may be easily used to minimize or prevent the emission of silica dust particles during the preparation of proppant for hydraulic fracturing.